Brightness control for a color cathode ray tube

ABSTRACT

Device for controlling the brightness of the trace of vectors on the screen of a cathode tube, which is more particularly polychromatic, comprising a clock, a vector generator and means for making the brightness of the trace vary. These means consist of frequency dividers connected to the output of the clock and supplying, to the vector generator, adjustable frequency pulses.

[111 3,786,483 [451 Jan. 1s, 1974 BRIGHTNESS CONTROL FOR A COLOR 340/324 A 3/1970 Bader et a1. 315/30 X 3,329,948 711967 Halsted...... 33.592 3 CATHODE RAY TUBE [75] Inventor:

Dusan Sinobad, Paris, France Assigneei Compagnie lndustrielle des P i Examiner-David L. Trafton Telecommu cati Attorney-Paul M. Craig, Jr. et a1. CIT-ALCATEL, Paris, France [22] Filed: Apr. 21, 1 972 [2]] App]. No.: 246,378

ABSTRACT Device for controlling the brightness of the trace of France..........1.................... 7114136 vectors on the screen of a cathode tube, which is more particularly polychromatic, comprising a clock, a vector generator and means for making the brightness of the trace vary. These means consist of frequency dividers connected to the output of the clock and supplying, to the vector generator, adjustable frequency pulses.

[58] Field of Search....-............. 340/324 A, 324 AD; 315/10, 22, 30

References Cited UNITED STATES PATENTS 3,130,346 Callick................ 315/22 7 Claims, 1 Drawing Figure BRIGHTNESS CONTROL FOR A COLOR CATHODE RAY TUBE The present invention relates in general to a device for controlling the brightness of the trace of vectors on the screen of a cathode ray tube. This invention applies more particularly to the regulating of the brightness of the trace of vectors on the screen of polychromatic cathode ray tubes, used in color display systems enabling for example observation of the traffic of various -mobile objects in a determined region of space.

Various data relating to the mobile objects moving in the region of space in question, and concerning, more particularly, their position, their identification, their speed or their altitude, in the case of airborne mobile objects, are transmitted to the observer installation, for example by a radar device or other detection or telemetering devices. The vectors which are to be traced on the screens of panoramic indicators are intended, for example, to show the direction and the speed of the mobile objects, or of the cartographic elements. These vectors constitute a sequence and thus form discontinuous lines or polygonal contours. They have welld'efined starting and ending points. It is particularly interesting to be able to observe the traffic of these various mobile objects by means of traces of varying brightness, or of different colors with brightness which can be regulated, in order to avoid any possible confusion between the paths of the different mobile objects.

Known devices making it possible to obtain such results generally comprise:

A vector generator, which receives, from a calculator, binary data concerning the directing parameters of the vectors to be displayed. This vector generator comprises:

A binary counter whose binary output level varies as a function of the data received at its inputs;

A digit-analogconverter, connected to an output of the vector generator. The analog signal supplied by the output of that converter depends on the binary output electron beam, a clock supplying control pulses to the said vector generator, characterized in that it comprises means for varying the frequency of the control pulses.

Merely by way of a non-limiting illustration, an example of the implementing of the device according to the invention will be described with reference to a diagrammatic figure.

This device comprises:

A vector generator 1 receiving, at its inputs 2 and 3, respectively, data X and Y concerning the directing parameters of the vector to be displayed. This data Xand t Y is, for example, the lengths X and Y of the projections of the vector in question on each of the axes of the coordinates of a Cartesian system. These parameters are expressed in binary form and come from a calculator. I i

The vector generator also receives, at its inputs, 4 and 5 respectively, the data X0 and Y0 concerning the starting point of the vector to be displayed. A clock 6, supplying at its output 7, controlpulses for the generator 1, these pulses arriving at an input 9 of that generator; and means 8, making it possible to vary the fret quency of the clock pulses arriving at the input 9 of the level of the counter. It is this analog signal, characteristic of the vector to be traced, which is applied, for example, to a plate for deflecting the electronic beam of the cathode ray tube enabling observation;

A clock which controls the vector generator by fixed recurrence frequency pulses. f

in devices of this type, the variation in the brightness of the trace on the screen is obtained by varying the voltage applied to the cathodeof the cathode ray tube, this causing a modification in the intensity of the electron beam. The frequency of the clock pulses being constant, two vectors of equal length are traced at the same speed.

For monochromatic systems, this variation in the voltage has'thedisadvantage of causing poor focusing of the light spot on the screen.

For polychrornatic systems, the variation of that voltage also causes poor focusing of the spot. Two vectors of equal length and of two different colors being traced at the same speed, these vectors will appear with a different brightness according to the color, the vectors traced in red being less bright than the vectors traced in green. Indeed, the colored vector, which requires, for its trace, the lowest acceleration voltage, is less bright than the others. Moreover, it remains very difficult to obtain good focusing for colors requiring a low generator.

The operation of the device will be better understood by means of the following explanations, given with reference to the accompanying diagram.

A constant'voltage V is applied to the cathode 33 of the cathode ray tube 29. The speed of the trace of a vector having a given length is proportional to the fre* quency of the control pulses coming from the clock 6. It is supposed that the Whenelt electrode 38 of the tube 29 is brought to a fixed reference potential, and the voltage V represents the difference in potential between the cathode and the Whenelt electrode.

The parameters X, Y, X0, Y0, of the vector to be traced come from a calculator, in binary form, to the inputs 2, 3, 4, 5 of the generator I. This generator supplies, at its outputs 25 and 26, analog signals characteristic of X0, X, and Y0, Y, applied, for example,

respectively, to the horizontal deflection plates 28 and vertical deflection plates 27, of the cathode ray tube 29. Another horizontal plate 30 and another vertical plate 31, each brought to a reference potential, have been diagrammatically shown in the figure. It is quite evident that in the example chosen, the deviation of the electron beam is electrostatic, but a magnetic deviation would be quite appropriate.

The vector generator comprises:

A binary frequency multiplier 16, which receives,

from the calculator, at its inputs 2 and 3, the binary data X and Y, and at its input 9, the control pulses coming from the clock, and adapted for modifying the speed of the trace;

A bidirectional counter 19 receiving, at its inputs 4, the binary data concerning X0, and at its input 35, the binary data X. It supplies, at its outputs, binary data concerning Xo, X, which is transmitted to the digit analog converter 21. This converter supplies to an amplifier 2.3, an analog signal, which, at the output 25 of that amplifier, controls the vertical deflection plate 27 of the cathode ray tube 29.

A bidirectional counter 20 receiving, at its inputs 5, the binary data concerning Y0, and at its input 36, the binary data Y. lt supplies, at its outputs, binary data concerning Yo, Y, which is transmitted to the digitanalog converter 22. This converter supplies, to the amplifier 24, an analog signal, which, at the output 26 of that amplifier, controls the horizontal deflection plate 27 of the cathode ray tube 29.

in a monochromatic tracer system, the voltage V applied at 32 to the cathode 33 of the cathode ray tube 29, is kept constant. For a vector of a given length, and to obtain a brighter trace, for example, the frequency of the clock pulses controlling the generator 1, is decreased through means 8 provided for that purpose. This is done in order to obtain a slower scanning of the screen, this causing an increase in brightness.

in a trichromatic trace system, for example, the color of the vector to be traced is obtained by applying to the cathode 33 of the tube 29, a particular voltage between the cathode and the Whenelt electrode for each required color. To vary the brightness of the trace, it is sufficient as previously indicated, to modify the clock pulse frequencies which arrive at the input 9 of the generator 1.'As an example, to trace three vectors having the same length, the one being red,- the other yellow,

and the last green, and the red vector being the dimmest, and to obtain an equal brightness on these three traces, the red vector must be traced more slowly than the green. The frequency of the clock pulses arriving at the generator must therefore be increasing, going from red to green.

The means 8 for making the clock pulse frequency vary, and thus for making the brightness of the trace vary on the screen of the cathode ray tube 29 comprise:

Binary frequency dividers l and ll, connected in series with the clock 6. Their number has been limited to two, but it is obvious that several other dividers could have been used. It is also quite obvious that the connection of the dividers could have been connected in parallel to the clock output; logic gates l2, l3, 14 of the AND" type, each gate having two inputs; one input of the gate 12 is connected to the clock and its other input receives a control signal 34. The gate 13 has one input connected to the output of the first frequency divider l0, and its other input receives a control signal 34. Lastly, the gate 14 has one input connected to the output of the second frequency divider ll, its other input receiving a control signal 34;

A logic gate 15 of the OR type connected by its inputs to the output of the gates 12, 13, 14, the output of that gate being connected to the input 9 of the vector generator.

In the case of a trichromatic trace, the red, to be brighter, must be traced more slowly than the green, hence, based on low-frequency clock pulses. The gate 14 will be opened by means of a control signal 34, for

the control pulse frequency of the generator to be that of the pulses which appear at the output of the second divider 11. The yellow will be traced, controlling the generator with pulses whose frequency is that of the output pulses of the first divider 10. This is obtained by opening the gate 13 controlled by a signal 34. Lastly, the green is traced directly, based on the frequency of the clock pulses, that is, with the greatest scanning speed, the opening of the gate 12"being controlled.

One advantage of the device is that the cathode voltage V is fixed at a constant value for each color. To modify the brightness of a trace, it is no longer necessary to subject that voltage to fluctuations about an average value. The focusing of the spot on the screen, and hence the clearness of the trace, are improved. The reliability of the system is, moreover, increased, due to the fact that that voltage on the cathode remains constant for each color. It is no longer necessary to slow the operation for the tracing of vectors whose color corresponds to good focusing. it is sufficient to decrease the trace speed, only for colors which require it.

It is quite obvious that the means making it possible to vary the frequency of the pulses arriving at the generator, and which are described in the example of the implementing of the device according to the invention could be replaced by equivalent means producing the same technical effect.

What is claimed is:

1. Device for controlling the brightness of the trace of vectors on the screen of a cathode ray tube, comprising vector generator means responsive to input signals representing the directing parameters of the vectors to be traced for supplying at its output an analog beam defiection control signal, a clock supplying control pulses to drive said vector generator, and frequency control means for varying the frequency of the control pulses provided by said clock, wherein said frequency control means for varying the frequency of the control pulses comprises a succession of frequency dividers connected to the output of said clock, a plurality of AND gates each receiving on one respective input the output signal of a respective divider, a second input of each gate receiving an individual opening control signal, and an OR gate having its inputs connected to the output of each of said AND gates, the output of said OR gate supplying frequency adjusted control pulses to said vector generator means.

2. Device according to claim 1 wherein said frequency dividers are connected in series with the output of the said clock.

3. Device according to claim 1 wherein said frequency dividers are connected in parallel to the output of the said clock.

4. Device according to claim 1 wherein said vector generator means includes a binary frequency multiplier receiving binary signals representing the X and Y parameters in Cartesian coordinates of the data to be displayed and said control pulses, a pair of bidirectional counters connected to receive respective outputs from said binary frequency multiplier relating to the respective X and Y parameters and binary signals representing the starting point in Cartesian coordinates of the data to be displayed, a respective digit-analog converter connected to the output of said bidirectional counters, the outputs of said respective converters being connected to the horizontal and vertical deflection apparatus of said cathode ray tube.

5. Device according to claim 4 wherein said frequency dividers are connected in series with the output of the said clock.

6. Device for controlling the brightness of the trace of vectors on the screen of a cathode ray tube, comprising vector generator means responsive to input signals representing the directing parameters of the vectors to be traced for supplying at its output an analog beam deflection control signal, a clock supplying control pulses to drive said vector generator, and frequency control means for varying the frequency of the control pulses provided by said clock, wherein said frequency control means includes means for varying the frequency of said control pulses to three distinct levels in response to the application thereto of three distinct control signals.

7. Device for controlling the brightness of the trace spective color traced in said cathode ray tube. 

1. Device for controlling the brightness of the trace of vectors on the screen of a cathode ray tube, comprising vector generator means responsive to input signals representing the directing parameters of the vectors to be traced for supplying at its output an analog beam deflection control signal, a clock supplying control pulses to drive said vector generator, and frequency control means for varying the frequency of the control pulses provided by said clock, wherein said frequency control means for varying the frequency of the control pulses comprises a succession of frequency dividers connected to the output of said clock, a plurality of AND gates each receiving on one respective input the output signal of a respective divider, a second input of each gate receiving an individual opening control signal, and an OR gate having its inputs connected to the output of each of said AND gates, the output of said OR gate supplying frequency adjusted control pulses to said vector generator means.
 2. Device according to claim 1 wherein said frequency dividers are connected in series with the output of the said clock.
 3. Device according to claim 1 wherein said frequency dividers are connected in parallel to the output of the said clock.
 4. Device according to claim 1 wherein said vector generator means includes a binary frequency multiplier receiving binary signals representing the X and Y parameters in Cartesian coordinates of the data to be displayed and said control pulses, a pair of bidirectional counters connected to receive respective outputs from said binary frequency multiplier relating to the respective X and Y parameters and binary signals representing the starting point in Cartesian coordinates of the data to be displayed, a respective digit-analog converter connected to the output of said bidirectional counters, the outputs of said respective converters being connected to the horizontal and vertical deflection apparatus of said cathode ray tube.
 5. Device according to claim 4 wherein said frequency dividers are connected in series with the output of the said clock.
 6. Device for controlling the brightness of the trace of vectors on the screen of a cathode ray tube, comprising vector generator means responsive to input signals representing the directing parameters of the vectors to be traced for supplying at its output an analog beam deflection control signal, a clock supplying control pulses to drive said vector generator, and frequency control means for varying the frequency of the control pulses provided by said clock, wherein said frequency control means includes means for varying the frequency of said control pulses to three distinct levels in response to the application thereto of three distinct control signals.
 7. Device for controlling the brightness of the trace of vectors on the screen of a cathode ray tube, comprising vector generator means responsive to input signals representing the directing parameters of the vectors to be traced for supplying at its output an analog beam deflection control signal, a clock supplying control pulses to drive said vector generator, and frequency control means for varying the frequency of the control pulses provided by said clock, wherein said cathode ray tube is a polychromatic tube and said frequency control means includes means for varying the frequency of said control pulses to a different distinct level for each respective color traced in said cathode ray tube. 